Circular trimming knives



Oct. 11, 1955 E. HOLROYD ETAL CIRCULAR TRIMMING KNIVES 2 Sheets-Sheet 1 Filed June 5, 1952 Oct. 11, 1955 E. HOLROYD ETAL 2,719,991

CIRCULAR TRIMMING KNIVES Fiied June 5, 1952 2 Sheets-Sheet 2 United States Patent CIRCULAR TRIMMING KNIVES Eric Holroyd, Speke, Liverpool, and George Kenneth Bailey, Huyton Quarry, Lancaster, England, assignors to Dunlop Tire and Rubber Corporation, Buffalo, N. Y., a corporation of New York Application June 3, 1952, Serial No. 291,421

Claims priority, application Great Britain June 16, 1951 6 Claims. (Cl. 12--88) This invention relates to circular trimming knives.

It is an object of the present invention to provide circular knives suitable for trimming rubber and other materials and especially for trimming moulding spew from moulded rubber articles.

According to the invention apparatus for trimming rubber and other materials comprises a pair of rotatable circular trimming knives mutually disposed with their axes relatively inclined whereby a portion of a face of one knife adjacent to its periphery overlaps and contacts the corresponding portion of the other knife, means for urging the knives together so that they drivably contact and means for rotating one of the knives whereby the knives co-operate in order to trim the said material.

Preferably the contacting face of one knife is dished and the corresponding face of the other knife is chamfered, the contacting face of each knife and its peripheral face meeting to form a blunt edge. Preferably also means are provided for adjusting the amount by which the knife peripheries overlap.

The invention will now be described with reference to the accompanying drawings in which:

Figure 1 illustrates a pair of circular trimming knives,

Figure 2 is a longitudinal part cross-sectional view of apparatus for trimming moulding spew from a rubber shoe sole,

Figure 3 is an end elevational view of the apparatus shown in Fig. 2 in the direction of arrow X.

Fig. 4 is a section taken on line 4-4 of Fig. 2.

Fig. 5 is a section taken on line 5-5 of Fig. 2.

Fig. 6 is a section taken on line 6-6 of Fig. 2.

The knives illustrated in Fig. 1 will now be described. A dished circular trimming knife 1 is drivably mounted in the housing 2 and a chamfered circular trimming knife 3 is fully rotatably supported in a housing 4, the chamfered knife 3 being spring urged into driving contact with the dished knife 1.

The configuration of the dished trimming knife 1 will now be more particularly described. The knife is circular in shape and is provided with a hub portion 5 and a dished portion 6. The peripheral portion 7 of the knife tapers towards the peripheral face 8 which is ground at right angles to the concave surface 9 so that a blunt angle is formed at the junction of the concave surface 9 and the ground peripheral face 8.

The configuration of the chamfered trimming knife 3 will now be more particularly described. The knife is cricular in shape and is provided at its periphery with two chamfered faces 10 and 11 mutually disposed at 90 and each inclined at an angle to the radially extending faces of the knife so that a circumferentially extending blunt edge is formed on the knife periphery.

The chamfered and dished trimming knives are formed so that the peripheral portion of said knife does not taper acutely to a sharp thin cutting edge, but is formed so that the knife at its peripheral extremity is comparatively thick, the inclined faces which meet to form the cutting edge being disposed so as to include a blunt angle.

The angle at which the concave surface 9 of the dished knife 1 is formed relative to the knife axis and the angle at which the chamfered face 10 of the chamfered knife 3 is formed relative to the knife axis is. such that, when the knives are mounted with the concave surface 9 and the chamfered face 10 in overlapping contact as illustrated in Fig. 1, the faces are in contact over substantially the whole of the overlapping area.

The concave surface 9 and the chamfered face 10 may be spherically ground or may be lapped so that the contacting surfaces of the knives lie on a surface of revolution generated by rotation of the line 12 (shown in Figure 1) about an axis passing through the point of intersection of the axes of the knives 1 and 3.

Apparatus for trimming moulding spew from a rubber sole moulded integrally with a shoe upper will now be described with reference to Figures 2 and 3. The apparatus comprises a frame 13 designed to be attached to a work bench and carrying a sprocket wheel 14 to be driven for instance by an electric motor and a detachable unit 15 comprising a straight arm 16 on which a chamfered trimming knife 17 is mounted and a cranked arm 18 on which the'dished knife 19 is mounted, the cranked arm 18 being carried by the straight arm 16 and being rotatable about the arm to allow for adjustment as will be later described.

The frame 13 comprises two side plates 20 and 21 spaced apart by distance pieces 22, each side plate housing a ball bearing (23 and 24), the bearings supporting a rotatable shaft 25 on which the sprocket wheel 14 is mounted. One end of the shaft projects beyond the side plate 21 and carries a half coupling 26. The half coupling 26 is provided with a plane face at a right angle to the axis of the shaft and a diagonal slot 26a in this face in which is slidably mounted a rib 26b of an intermediate coupling disc 260. The opposite side of the disc 260 is provided with a rib 26d positioned at a right angle to the rib 26b, that is, around the axis of the coupling. The rib 26d is, in turn, slidably engaged in a diagonally transverse groove of a half coupling 27 rigidly mounted on a driving spindle 28 for the chamfered knife 17. This type of coupling, which is not novel, permits the driving of one shaft, such as 28, from a driving shaft 25 even when their axes are displaced a limited amount from exact alignment. Other known couplings of similar function may be used in place of that shown.

The straight arm 16 comprises an annular support 29 having a flange 30 at one end through which it is rigidly but detachably connected to the support 13 by means of a collar 31 which is in screw-threaded engagement with an externally threaded annular projection 32 attached to the side plate 21.

The diameter of the support is substantially reduced at a short distance from the flange to form a bearing surface 33 of uniform diameter, extending over about a quarter of the length of the support, for a rotatable sleeve 34 integral with the cranked arm. The sleeve is retained in position on the support by a screw-threaded nose cap 35 engaging with a correspondingly screwthreaded portion of the support. The outer surfaces of the support 29, sleeve 34 and nose cap 35 gradually decrease in diameter so that the profile of the unit 15 tapers uniformly from a position adjacent the flange 30 to the end of the nose cap 35 adjacent to the knife.

The driving spindle 28 is located within a cylindrical cavity 38 in the straight arm 16 by means of eccentric bearing bushes 36 and 37 located at each end of the cavity. The function of these eccentric bushes is for adjustment of the knives as will be described hereinafter.

The driving spindle 28 is provided with a counterbore 39 which extends from the end near the chamfered trimming knife 17 to a position at a short distance from the half-coupling 27, and an inner spindle 40, to which the chamfered trimming knife 17 is fixed by means of a screw 41, extends slightly over half way along the counterbore and is a sliding fit therein. The end of the inner spindle within the cavity has a reduced diameter portion 42 and an annular spring locating member 43 having a similar reduced diameter portion 44 is fitted at the blind end of the counterbore. A compression spring 45 is located in the counterbore between the spring locating member 43 and the inner spindle 40, the ends of the spring being carried by the reduced diameter portions 42 and 44. The drive is transmitted from the driving spindle 28 to the inner spindle 40 by means of a peg 46 attached thereto and slidable in an axially extending slot 47 formed in the wall of the counterbore portion of the spindle 28. The inner spindle 40 is therefore free to move outwards to a predetermined extent under the influence of the compression spring 45 to maintain the trimming knives 17 and 19 in engagement.

The end of the cranked arm 18 which carries the dished trimming knife 19 is formed as a cylindrical casing 48 open at both ends. The end 49 adjacent the straight arm 16 is bevelled internally to receive the knife 19, slight clearance being allowed between the adjacent faces of the knife and casing. The knife 19 is mounted so that its rim 50 projects beyond the end of the casing.

The other end of the casing is closed by a detachable annular end plate 51. The reduced diameter screwed end 52 of an adjustable sleeve 53, projects through the annular end plate 51, the larger diameter portion of the sleeve being located within a fixed sleeve 54 forming a liner for the wall of the casing. The adjustable and fixed sleeves 53 and 54 are in screw-threaded engagement over a portion of their lengths 55. The axial position of the adjustable sleeve 54 can therefore be varied relative to the casing 48 and is fixed by means of a locknut 56 engaging with the screwed end 57 of the sleeve.

A spindle 58 to which the dished knife 19 is attached by means of a screw 59, is rotatably located in an eccentric axially extending bore 60 provided in the adjustable sleeve 53, a ball bearing 61 being provided between the base of the spindle 58 and a thrust plate 62 located in the base of the sleeve 53. The adjustment of the eccentrically bored sleeve 53 and the bushes 36 and 37 and the operation of the apparatus for trimming moulding spew from the edges of'moulded rubber shoe soles will now be described.

The apparatus is first of all adjusted so that sufficient of the surfaces of the dished'and chamfered trimming knives 17 and 19 are in contact for efficient trimming to take place.

Adjustment may be effected either by rotating the cranked arm 18 relative to the straight arm 16 or by rotating the eccentrically bored sleeve 53. It may be necessary to effect both adjustments.

Rotation of the cranked arm 18 causes more or less of the peripheral surfaces to come into contact on account of the fact that the chamfered trimming knife 17 is eccentrically mounted relative to the cranked arm 18 by means of the eccentric bushes 36 and 37.

Rotation of the eccentrically bored bush 53 also causes more or less of the peripheral surfaces of the knives to come into contact as will readily be appreciated.

When effecting either of these adjustments it is essential that the peg 46 attached to the inner spindle 40 should remain slidable in its axially extending slot 47 and not be hard-over at one end or other of this slot.

In order to commence trimming, the electric motor is started and the sprocket wheel 14 is rotated, the drive from which is transmitted through the half couplings (26, 27) to the driving spindle 28 from which it is transmitted to the inner spindle 40 and the chamfered knife 17 attached thereto. The chamfered knife 17 is held in close contact with the dished knife 19 by means of the compression spring 45 so that the dished knife is driven by frictional contact with the chamfered knife.

The shoe to be trimmed is then fed by hand so that the moulding spew is engaged by the knives 17 and 19 and trimmed close to the edge of the sole, the shoe being moved relative to the knives by the operator.

In order to obtain a self-sharpening action of trimming knives in accordance with the invention, the hardness to which the driving knife, the chamfered knife in the embodiment just described, is tempered, is greater than that of the driven knife. Thus the driving knife during rotation wears away the surface of the contacting driven knife and so maintains its periphery in a sharpened condition.

Although the trimming knives have been described in connection with the removal of the moulding spew from moulded rubber shoe soles, the knives may similarly be utilised for trimming spew from other moulded rubber articles. In addition, the knives may be used for trimming plastic and fabric material, the knives being driven by'means of apparatus similar in design to that hereinbefore described.

Having described our invention what we claim is:

1. Apparatus for trimming rubber and other materials which comprises a rotatable cutter having a dished peripheral marginal face, a second rotatable cutter having a chamfered'marginal face complementary to said dished marginal face of said first cutter, and a support mounting said cutters rotatably on intersecting axes of rotation with the peripheries of said cutters intersecting and the dished and champfered faces in contact, said support having'a housing and an eccentrically bored bush in which one of said cutters is rotatably mounted, said bush being rotatable in said housing to adjust the amount by which the cutter peripheries overlap.

2. Apparatus for trimming rubber and other materials which comprises a rotatable cutter having a dished peripheral marginal face, a second rotatable cutter having a chamfered marginal face complementary to said dished marginal face of said first cutter, a support mounting said cutters rotatably on intersecting axes of rotation with the peripheries of said cutters intersecting and the dished and chamfered faces in contact, said support comprising supporting arms at an angle to each other, one for each cutter, driving means for said second cutter, said first cutter being freely rotatable, and a spring pressing said second cutter into engagement with said first cutter.

I 3. Apparatus for trimming rubber and other materials which comprises a supporting arm, a driven spindle mounted on said supporting arm, a cutting disc fixed on said spindle and having a chamfered marginal face, a second arm mounted on said supporting arm to swing about said arm on an axls eccentric to the axis of said spindle and a disc rotatably mounted on said arm and having a dished marginal face engaging the chamfered marginal face of said first cutting disc in overlapping relation with the peripheries of said discs intersecting whereby said second cutting disc is rotated by said first cutting disc.

4. The apparatus of claim 3 having a spring to press said first cutting disc against the marginal face of said second cutting disc.

5. The apparatus of claim 3 in which said second arm is provided with a rotatable bush and in which said second cutter is rotatably mounted in said bush on an axis of rotation eccentric to the axis of rotation of said bush.

6. The apparatus of claim 2 in which the second cutter is secured to aplunger, and having a counterbored driving shaft in which said plunger is slidably keyed and in which the spring is mounted between the plunger and shaft.

References Cited in the file of this patent UNITED STATES PATENTS 577,985 Koegel Mar. 2, 1897 6 Lingenfelter Nov. 5,1907 Lennox Apr. 12, 1910 Mason Sept. 20, 1927 Hoopes Mar. 11,1930

FOREIGN PATENTS Germany Sept. 15, 1896 

